Computing devices, such as notebook computers, personal digital assistants, mobile communication devices, portable entertainment devices (e.g., handheld video game devices, multimedia players) may include user interface devices that facilitate interaction between a user and the computing device.
One type of user interface device that has become more common operates by way of capacitance sensing. A capacitance sensing system may include a touch screen, touch-sensor pad, a touch-sensor slider, or touch-sensor buttons, and may include an array of one or more capacitive sensor elements (also referred to as sensor electrodes). Capacitive sensing typically involves measuring, through sensor signals (e.g., increases or decreases in electrode responses), a change in capacitance associated with the capacitive sensor elements to determine a presence/proximity of a conductive object (e.g., a user's finger or head) relative to the capacitive sensor elements. A goal of touch screen proximity sensing is to provide high proximity object detection distance (e.g., distance of an approaching head when a user is answering a phone call) and normal finger detection capability (e.g., normal use of the touch screen to interact with an electronic device) at the same time.
However, with high detection distance of proximity objects, there is a possibility that approaching fingers are detected as a proximity object. Thus, there is a need for touch screen devices that are able to discriminate between signals caused by approaching fingers and a proximity objects (such as a head). Another problem with proximity detection is that, if sensitivity is decreased to avoid confusing approaching fingers with a proximity object, an ear creates finger-like touch screen signals, so a fast approaching ear can be detected as a finger touch instead of part of a proximity object (e.g., a head).